This invention relates to compositions of t-butyl peroxymaleic acid containing solid diluents and methods of using these compositions in polymer modification; more particularly this invention relates to compositions of dry, solid, free-flowing solid peroxyesters having melting points greater than 30xc2x0 C., and certain salts of organic acids having melting points greater than the melting points of the peroxides to which they are added, with optionally a dust suppressant, and optionally a free-flowing aid.
In particular, this invention comprehends processes for modifying polymer and copolymer compositions, by using the solid peroxide formulations to graft monomers, attach peroxide decomposition products, or intentionally degrade the polymer or copolymer (for example, such reactions known as vis-breaking, controlled rheology, or rheology modification).
Many diluted peroxide compositions are described in the prior art, although none of them teaches the instant invention.
U.S. Pat. No. 3,538,011 describes solid, free-flowing, stabilized compositions containing organic peroxides and organic fillers and the methods for the production of these compositions. Organic peroxides employed in this patent for these organic peroxide/organic filler compositions are aromatic and aliphatic diacyl peroxides, ketone peroxides and peroxyesters that are solid at room temperature whereas, the fillers employed are solid plasticizers that are soluble in polyester resin masses and are solid at room temperature, such as dicyclohexyl phthalate (m.p. 63-5xc2x0 C.). These organic fillers are claimed to reduce the explosiveness and the shock sensitivity of the organic peroxides employed.
U.S. Pat. No. 4,387,044 describes safe, dry, free-flowing solid peroxide/unsubstituted or alkyl substituted benzoic acid compositions prepared by mixing the solid peroxide, such as a diacyl peroxide, dialkyl peroxydicarbonate, dialkyl peroxide or alkylidene diperoxide, which melts about 30xc2x0 C. with solid benzoic acid or an alkyl substituted benzoic acid, which melts above 40xc2x0 C. The patent teaches that these compositions are useful as initiators for the polymerization of ethylenically unsaturated monomers, such as styrene, and for curing of unsaturated polyester resins and diethylene glycol bis(allyl carbonate). The solid peroxide compositions exhibit improved safety characteristics such as delayed ignition times when in contact with flame and increased thermal stabilities compared to prior art formulations.
U.S. Pat. Nos. 2,453,070 and 2,453,071 disclose impact shock-desensitized dibenzoyl peroxide compositions in which the preferred compositions are desensitized with 2-10% aliphatic carboxylic acids such as lauric acid and less preferably desensitized with 5% phthalic acid and 5% salicylic acid.
The prior art also is replete with many peroxide paste compositions containing one or more organic safety liquids and water. Although these peroxide pastes and suspensions are described to be safe, none of them teach a safe, free-flowing solid peroxide composition of the present invention that have been found to be significantly more permanently stable than similar prior art formulations and considerable more resistant to burning ignition. Moreover, the filler in the instant invention has no detrimental effects on the rate of solution of, or the polymerization or curing efficiency of the formulation in ethylenically unsaturated monomers, such as styrene or in unsaturated polyester resins.
None of the above art references describes the instant invention. Although t-butyl peroxymaleic acid is mentioned in two of the references, no examples were described using this peroxide. Yet there is still a need for appropriate commercial formulations of t-butyl peroxymaleic acid. This is primarily due to safety and handling considerations. Packaging and shipping regulations for this peroxide restrict transport of pure t-butyl peroxymaleic acid to 25 kilogram packages for safety reasons (see Recommendations on the Transport of Dangerous Goods, Model Regulations, 10th revised edition, United Nations, New York, 1997). This makes using this peroxide on a commercial scale difficult, since large quantities must be purchased and stored and handled in relatively small packages. A viable alternative is to formulate diluted peroxide that exhibits safety characteristics that will permit shipment and handling of larger quantities. As the prior art indicates, there are many possible diluents, yet no one diluent meets the needs of all end use applications. The instant invention is for novel, extended formulations of t-butyl peroxymaleic acid that are acceptable for use in many commercial applications.
This invention provides a safe, free-flowing, solid, peroxide formulation consisting essentially of 40-85% by weight of solid t-butyl peroxymaleic acid, 15-60% by weight of a solid diluent selected from salts of structure (Rxe2x80x94CO2)xM(+x) wherein x is an integer selected from 1, 2 or 3 and wherein R is a linear or branched alkyl group of 5-30 carbon atoms optionally substituted with one or more hydroxy (xe2x80x94OH) groups, or a linear or branched mono-, di- or polyalkenyl group of 5-20 carbons and when x is 1, M is a metal ion chosen from lithium, sodium, potassium, and when x is 2, M is a metal ion chosen from calcium, magnesium, lead, barium, cadmium and zinc, and when x is 3, M is aluminum, salts of structure CO2(M(+X))y wherein x and y are integers selected from 1 or 2, wherein when y is 1, x is 2 and M is a metal ion selected from calcium, magnesium, lead, barium, cadmium and zinc, and when y is 2, x is 1 and M is a metal ion selected from lithium, sodium, potassium, and optionally 0-2% by weight of a dust suppressant, and optionally 0-2% of a free-flowing aid. Hydrates of the salts may be used. Mixtures of salts may be used.